The programme, Shallow Grave, marks the return of 24 Hours In Police Custody, the Bafta-nominated Channel 4 series that probes some of the most challenging cases handled by Bedfordshire and Cambridgeshire police’s major crime unit.

For more than three years, cameras recorded the activities of the detectives to produce a real-life crime drama at its most compelling.

Natalia was killed by her ex-husband Gerald Doherty in 2003 and her body left under a pile of rubble in the back garden of a house in Icknield Way, Luton.

Doherty travelled to Scotland to speak to his older brother Joseph – but not long after he committed suicide in July 2003.

Joseph Doherty, of Port Glasgow, Renfrewshire, later pleaded guilty to perverting the course of justice and was handed a suspended jail sentence for “propagating a false account regarding the circumstances of her death”

Despite the detail provided by Joseph, police are convinced Gerald did not act alone.

Detectives at the crime scene where Natalia’s body was found buried beneath rubbish

Detective Inspector Jerry Waite, who led the investigation, said: “It’s not as easy to get rid of a body as people think.

“One of the hardest jobs for any murderer is how to get rid of the body.”

In a dramatic twist in 2015, detectives revealed a new piece of evidence – a statement from a family member claiming Joseph had hinted to another relative that he knew where Natalia’s body was concealed – in his brother’s Daniel’s garden.

Joseph is seen in the documentary footage looking stony-faced when asked about the statement.

Production Company. Channel 4 images must not be altered or manipulated in any way. This

There was suspicion that Joseph and his brother Daniel (pictured being checked into custody), who had been one of the last people to see Natalia alive, may have been involved in covering up Natalia’s disappearance